The invention relates to the field of braking systems, particularly those braking systems that utilize linkages to transmit brake-generated loads from a wheel and brake assembly to a braked vehicle.
Vehicle braking systems are one of a class of mechanisms that can be induced to vibrate by the action of friction. In some situations, the vibration may become unstable and grow to levels severe enough to cause excessive noise, passenger discomfort, and/or structural failure of system components. Part of the art of designing such systems lies in increasing the stabilizing effects of damping within and between the components of the system to counteract the destabilizing effects of braking friction.
The invention applies to any member of a general class of braking systems that use linkages to transmit brake-generated loads from the wheel and brake to the braked vehicle. It is particularly useful with multi-brake aircraft landing gear systems. In such a landing gear, the wheel and brake assemblies are typically mounted in pairs on two or more tandem axles, which are in turn fixed to a "bogie" or "truck" beam that pivots about a point on the inner cylinder of the landing gear's shock strut. The brake torque generated by each of the fore and aft assemblies is reacted by forces at its axle and through a brake rod that links the brake to the inner cylinder of the landing gear at a point above or below the bogie pivot. The fore brake rods act in compression and the aft rods act in tension to transmit braking forces to the bogie. For each assembly, the rod forms one of the four links of a parallel four-bar linkage that operates in the pitch plane of the aircraft.
The dominant modes of friction-induced vibration in aircraft brakes are "squeal" (a torsional oscillation of the non-rotatable brake parts) and "whirl" (a rotating bending oscillation). During both modes of vibration, an oscillating load is superimposed on the mean compression or tension loads carried by the brake rods that may cause the rod to bend. Workers in the art have recently attempted to solve the brake vibration problem in various ways, including providing an axial coulomb damper in a brake rod. The brake rod essentially acts as a shock absorber. This solution did not prove to be entirely satisfactory.
A simple, lightweight, inexpensive, and effective solution to the brake vibration problem is generally desired.